Here's something I just wrote to someone recovering from spasmodic dysphonia and wanting to develop his vocal abilities. I suggested singing.
The three basic ranges in music are loud/soft, fast/slow, and high/low. The basic idea would be to find your absolute most comfortable place in each, work to more fully inhabit and project that sound, and then slowly, carefully increase the comfort zone in each of those ranges.
Another less obvious range in music making is gestural. An off-beat genius by the name of Manfred Clynes organized that range as the "sentic cylcle": no-emotion, anger, hate, grief, love, sexual desire, joy, and reverence. The idea would be to practice expressing a variety of feelings you'd like to be able to communicate by your manner of speaking/singing.
Remember that speech and music and dance can be seen as a continuum. Some easy rhythmic movement while speaking/singing might be beneficial.